The present invention relates to an output signal circuit and, more particularly, to an output signal circuit capable of automatically detecting polarity to output signals with proper polarity.
Some output signals are of active high drive, while some are of active low drive. The polarities of output signals are usually defined in the specification of each special integrated circuit (IC) by designers of the IC. FIG. 1 shows a circuit diagram having pins of input and output signals in the prior art. When a system undergoes a power on reset or a hardware reset and a system driver stays, the output signals will accept commands of the driver to reflect proper polarities and show exact states, which includes driving a LED indication lamp, or turning on or off the power of accessory circuits.
When the polarity of the output signals of a special IC is fixed, the flexibility of design of the IC in system application circuits (e.g., direct drive of simple small-current LED indication lamp, drive of relay, or drive of power of more complex accessory circuit) will be limited. When system designers take into account components, cost, layout, and materials, if the polarity of output signals of IC is fixed, opportunity of usage of the IC in some situations may be lost. Especially, in more complex drive modules, when the polarity of output signals of an IC is reversed, the IC cannot be used. An inverter must be added so that the IC can be used. However, this kind of way will increase the manufacturing cost of drive module and trouble in preparing materials for production.
Accordingly, the present invention aims to propose an output signal circuit capable of automatically detecting polarity.
The primary object of the present invention is to provide an output signal circuit capable of automatically detecting polarity, whose input/output signal terminals have input and output functions simultaneously. When a system undergoes a power on reset or a hardware reset, the output signal circuit can be temporarily shut off, and the logic state of the signal terminal can be imported. After reset and a driver stays in the IC, output signals with proper polarity will be outputted according to the driver""s commands, thereby enhancing the flexibility of usage of the IC in various kinds of driver modules.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings, in which: